feat: add blake3 160, 192 & 256 bits

closes #6

Cargo.toml

@@ -15,10 +15,11 @@ name = "hash"
 harness = false
 
 [features]
-default = ["std", "winter_crypto/default", "winter_math/default", "winter_utils/default"]
-std = ["winter_crypto/std", "winter_math/std", "winter_utils/std"]
+default = ["blake3/default", "std", "winter_crypto/default", "winter_math/default", "winter_utils/default"]
+std = ["blake3/std", "winter_crypto/std", "winter_math/std", "winter_utils/std"]
 
 [dependencies]
+blake3 = { version = "1.0", default-features = false }
 winter_crypto = { version = "0.4.1", package = "winter-crypto", default-features = false }
 winter_math = { version = "0.4.1", package = "winter-math", default-features = false }
 winter_utils = { version = "0.4.1", package = "winter-utils", default-features = false }

src/hash/blake/mod.rs

@@ -0,0 +1,230 @@
+use crate::{
+    ByteReader, ByteWriter, Deserializable, DeserializationError, Digest, ElementHasher, Felt,
+    FieldElement, HashFn, Serializable, StarkField,
+};
+use core::{
+    mem::{size_of, transmute, transmute_copy},
+    ops::Deref,
+    slice::from_raw_parts,
+};
+
+#[cfg(test)]
+mod tests;
+
+// BLAKE3 N-BIT OUTPUT
+// ================================================================================================
+
+/// N-bytes output of a blake3 function.
+///
+/// Note: `N` can't be greater than `32` because [`Digest::as_bytes`] currently supports only 32
+/// bytes.
+#[derive(Debug, Copy, Clone, Eq, PartialEq)]
+pub struct Blake3Digest<const N: usize>([u8; N]);
+
+impl<const N: usize> Default for Blake3Digest<N> {
+    fn default() -> Self {
+        Self([0; N])
+    }
+}
+
+impl<const N: usize> Deref for Blake3Digest<N> {
+    type Target = [u8];
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl<const N: usize> Serializable for Blake3Digest<N> {
+    fn write_into<W: ByteWriter>(&self, target: &mut W) {
+        target.write_u8_slice(&self.0);
+    }
+}
+
+impl<const N: usize> Deserializable for Blake3Digest<N> {
+    fn read_from<R: ByteReader>(source: &mut R) -> Result<Self, DeserializationError> {
+        source.read_u8_array().map(Self)
+    }
+}
+
+impl<const N: usize> Digest for Blake3Digest<N> {
+    fn as_bytes(&self) -> [u8; 32] {
+        // compile-time assertion
+        assert!(N <= 32, "digest currently supports only 32 bytes!");
+        expand_bytes(&self.0)
+    }
+}
+
+// BLAKE3 256-BIT OUTPUT
+// ================================================================================================
+
+/// 256-bit output blake3 hasher.
+pub struct Blake3_256;
+
+impl HashFn for Blake3_256 {
+    type Digest = Blake3Digest<32>;
+
+    fn hash(bytes: &[u8]) -> Self::Digest {
+        Blake3Digest(blake3::hash(bytes).into())
+    }
+
+    fn merge(values: &[Self::Digest; 2]) -> Self::Digest {
+        Self::hash(prepare_merge(values))
+    }
+
+    fn merge_with_int(seed: Self::Digest, value: u64) -> Self::Digest {
+        let mut hasher = blake3::Hasher::new();
+        hasher.update(&seed.0);
+        hasher.update(&value.to_le_bytes());
+        Blake3Digest(hasher.finalize().into())
+    }
+}
+
+impl ElementHasher for Blake3_256 {
+    type BaseField = Felt;
+
+    fn hash_elements<E>(elements: &[E]) -> Self::Digest
+    where
+        E: FieldElement<BaseField = Self::BaseField>,
+    {
+        Blake3Digest(hash_elements(elements))
+    }
+}
+
+// BLAKE3 192-BIT OUTPUT
+// ================================================================================================
+
+/// 192-bit output blake3 hasher.
+pub struct Blake3_192;
+
+impl HashFn for Blake3_192 {
+    type Digest = Blake3Digest<24>;
+
+    fn hash(bytes: &[u8]) -> Self::Digest {
+        Blake3Digest(*shrink_bytes(&blake3::hash(bytes).into()))
+    }
+
+    fn merge(values: &[Self::Digest; 2]) -> Self::Digest {
+        Self::hash(prepare_merge(values))
+    }
+
+    fn merge_with_int(seed: Self::Digest, value: u64) -> Self::Digest {
+        let mut hasher = blake3::Hasher::new();
+        hasher.update(&seed.0);
+        hasher.update(&value.to_le_bytes());
+        Blake3Digest(*shrink_bytes(&hasher.finalize().into()))
+    }
+}
+
+impl ElementHasher for Blake3_192 {
+    type BaseField = Felt;
+
+    fn hash_elements<E>(elements: &[E]) -> Self::Digest
+    where
+        E: FieldElement<BaseField = Self::BaseField>,
+    {
+        Blake3Digest(hash_elements(elements))
+    }
+}
+
+// BLAKE3 160-BIT OUTPUT
+// ================================================================================================
+
+/// 160-bit output blake3 hasher.
+pub struct Blake3_160;
+
+impl HashFn for Blake3_160 {
+    type Digest = Blake3Digest<20>;
+
+    fn hash(bytes: &[u8]) -> Self::Digest {
+        Blake3Digest(*shrink_bytes(&blake3::hash(bytes).into()))
+    }
+
+    fn merge(values: &[Self::Digest; 2]) -> Self::Digest {
+        Self::hash(prepare_merge(values))
+    }
+
+    fn merge_with_int(seed: Self::Digest, value: u64) -> Self::Digest {
+        let mut hasher = blake3::Hasher::new();
+        hasher.update(&seed.0);
+        hasher.update(&value.to_le_bytes());
+        Blake3Digest(*shrink_bytes(&hasher.finalize().into()))
+    }
+}
+
+impl ElementHasher for Blake3_160 {
+    type BaseField = Felt;
+
+    fn hash_elements<E>(elements: &[E]) -> Self::Digest
+    where
+        E: FieldElement<BaseField = Self::BaseField>,
+    {
+        Blake3Digest(hash_elements(elements))
+    }
+}
+
+// HELPER FUNCTIONS
+// ================================================================================================
+
+/// Zero-copy ref shrink to array.
+fn shrink_bytes<const M: usize, const N: usize>(bytes: &[u8; M]) -> &[u8; N] {
+    // compile-time assertion
+    assert!(
+        M >= N,
+        "N should fit in M so it can be safely transmuted into a smaller slice!"
+    );
+    // safety: bytes len is asserted
+    unsafe { transmute(bytes) }
+}
+
+/// Hash the elements into bytes and shrink the output.
+fn hash_elements<const N: usize, E>(elements: &[E]) -> [u8; N]
+where
+    E: FieldElement<BaseField = Felt>,
+{
+    // don't leak assumptions from felt and check its actual implementation.
+    // this is a compile-time branch so it is for free
+    let digest = if Felt::IS_CANONICAL {
+        blake3::hash(E::elements_as_bytes(elements))
+    } else {
+        E::as_base_elements(elements)
+            .iter()
+            .fold(blake3::Hasher::new(), |mut hasher, felt| {
+                hasher.update(&felt.as_int().to_le_bytes());
+                hasher
+            })
+            .finalize()
+    };
+    *shrink_bytes(&digest.into())
+}
+
+/// Owned bytes expansion.
+fn expand_bytes<const M: usize, const N: usize>(bytes: &[u8; M]) -> [u8; N] {
+    // compile-time assertion
+    assert!(M <= N, "M should fit in N so M can be expanded!");
+    // this branch is constant so it will be optimized to be either one of the variants in release
+    // mode
+    if M == N {
+        // safety: the sizes are checked to be the same
+        unsafe { transmute_copy(bytes) }
+    } else {
+        let mut expanded = [0u8; N];
+        expanded[..M].copy_from_slice(bytes);
+        expanded
+    }
+}
+
+// Cast the slice into contiguous bytes.
+fn prepare_merge<const N: usize, D>(args: &[D; N]) -> &[u8]
+where
+    D: Deref<Target = [u8]>,
+{
+    // compile-time assertion
+    assert!(N > 0, "N shouldn't represent an empty slice!");
+    let values = args.as_ptr() as *const u8;
+    let len = size_of::<D>() * N;
+    // safety: the values are tested to be contiguous
+    let bytes = unsafe { from_raw_parts(values, len) };
+    debug_assert_eq!(args[0].deref(), &bytes[..len / N]);
+    bytes
+}

src/hash/blake/tests.rs

@@ -0,0 +1,20 @@
+use super::*;
+use crate::Vec;
+use proptest::prelude::*;
+
+proptest! {
+    #[test]
+    fn blake160_wont_panic_with_arbitrary_input(ref vec in any::<Vec<u8>>()) {
+        Blake3_160::hash(vec);
+    }
+
+    #[test]
+    fn blake192_wont_panic_with_arbitrary_input(ref vec in any::<Vec<u8>>()) {
+        Blake3_192::hash(vec);
+    }
+
+    #[test]
+    fn blake256_wont_panic_with_arbitrary_input(ref vec in any::<Vec<u8>>()) {
+        Blake3_256::hash(vec);
+    }
+}

src/hash/mod.rs

@@ -1,5 +1,8 @@
 use crate::{ElementHasher, HashFn};
 
+mod blake;
+pub use blake::{Blake3Digest, Blake3_160, Blake3_192, Blake3_256};
+
 mod rpo;
 pub use rpo::Rpo256 as Hasher;
 pub use rpo::{INV_MDS, MDS};